A device of this kind is also known from the prior art as a phase adjuster or a camshaft adjuster inasmuch as the shaft to be adjusted is a camshaft, for example. However, the invention is not restricted to use as a camshaft adjuster but can be applied similarly to any rotating adjustment shafts, e.g. to adjustment shafts for adjusting the valve lift of mechanically variable valve mechanisms.
An adjusting device for a camshaft is disclosed by DE 41 01 676 A1, for example. It comprises an actuating element, which is operatively connected to the shaft to be adjusted and to a drive wheel via inner and outer splines. One set of splines is designed as helical toothing, and therefore an axial movement of the actuating element brings about an adjustment of the rotation angle position of the camshaft with respect to the drive element in accordance with the principle of inclined planes. In this case, the actuating element is actuated by an electric motor.
Concepts which employ one or more brake actuators to adjust the rotation angle position of a camshaft with respect to a drive element are furthermore known from the prior art. When a brake actuator is employed, adjustment can be brought about in only one direction of adjustment. For adjustment in the other direction, a spring can then be employed, for example. However, spring-actuated adjustment has the disadvantage that a continuously acting force is produced by the spring. Retention of a particular position of adjustment thus requires an opposing force, which must in turn be applied by the brake actuator. Accordingly, the spring force selected should be as low as possible. A high spring force, on the other hand, has an advantageous effect on the dynamics of the adjusting system. There is therefore a conflict if both a low retention force and high dynamics are to be ensured. The speed of adjustment of a spring-actuated adjusting system is furthermore dependent on the speed, load and temperature of the internal combustion engine, and therefore very great time differences are often achieved. Moreover, the achievable speed of adjustment is below that of a brake-actuated adjusting system.
EP 2 067 944 A1 has disclosed a device which employs two brake actuators to adjust the rotation angle position of the camshaft with respect to a drive wheel. The brake actuators serve to move an intermediate member axially, said intermediate member being coupled to a shaft section and to a drive wheel in such a way that the axial movement of the intermediate member brings about an adjustment of the relative rotation angle position of the shaft section with respect to the output wheel. Here, the shaft section serves merely to extend the camshaft. For coupling to the intermediate member, each brake actuator comprises a rotating annular coupling member, which is operatively connected to the intermediate member in such a way that a change in the rotational speed of a coupling member due to the actuation of a brake actuator brings about a difference in speed and hence an axial movement of the intermediate member. Alternate actuation of the brake actuators thus leads to braking of one or the other coupling member, with the result that a movement of the intermediate member takes place in one or the other direction of adjustment. By means of the axial movement of the intermediate member, the rotation angle position of the camshaft with respect to the drive wheel is finally adjusted.